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Posted: August 9, 2004

Science of Sport: The Effects of Blood Donation on Endurance Athletes

Presented below are four essays on the effects of donating blood on endurance athletes

1. How do periodic reductions in hemoglobin affect an athlete's ability to train?

From: Inside Triathlon

Blood is a complicated tissue with many different roles. When you donate blood, you give up a pint of fluid containing mostly water along with various proteins and cells in solution. During high-intensity endurance activities however, it is hemoglobin, found within our red blood cells, that is most important.

Hemoglobin delivers oxygen to our tissues, and when we exercise our muscles require increased amounts of oxygen. If we lack sufficient hemoglobin, anaerobic, or without oxygen, metabolism will ensue (producing lactic acid) at even seemingly moderate levels of intensity.

Donating a pint (450cc) of blood results in a depletion of about 10 percent of your total blood volume. Of that, only about 160cc are red blood cells. The fluid component, the remaining 290cc, is replaced within hours, but the red blood cell replacement takes about two months, (which is why you may not donate more often than every two months). What then are the lasting effects of this red blood cell loss?

Assuming that your cardiac output (the amount of blood pumped by the heart) remains constant, a drop in hemoglobin concentration associated with donating blood will reduce your oxygen delivery to working muscles by 10 percent. Still, when you are at rest, or even during moderate levels of exercise, oxygen delivery, even at this decreased capacity, far outpaces demand.

However, once you reach a heart rate that is around 5 to 10 percent below your usual anaerobic threshold, your body's demand for oxygen will outpace its supply. For example, if your metabolism typically becomes anaerobic at a heart rate of 170, then after donating blood you will become anaerobic at a heart rate of between 157 and 164 beats per minute. This value will fluctuate because your hemoglobin level will be rising slowly each day, thus the most significant effect will be felt in the first few days after donating.

The key to recovery is ensuring your body has the necessary building blocks -- specifically protein and iron -- to replace the lost hemoglobin. For most people, eating a balanced diet with adequate protein and iron intake is sufficient. For some, however (specifically vegetarians and some women), iron supplementation may be required. Talk to your doctor to determine if this kind of supplementation may be right for you.

Dr. Jeffrey Sankoff, MD, FRCP(C), is a triathlete and ER physician based in Denver, Colorado.

2. Donating Blood - What Active People Need to Know

From: Physician and Sportsmedicine

Competitive athletes and those who work out often wonder if donating a pint of blood will impair their athletic performance or fitness goals. They have good reason to wonder. After all, blood donation can influence hydration status and the oxygen-carrying ability of red blood cells.

In some situations, athletic pursuits and the public's need for blood are cast as competing interests--for example, when coaches advise student-athletes to decline donation requests. A recent blood drive sponsored by the student council at Totino Grace High School in Fridley, Minnesota, became mildly controversial when some athletes decided not to donate. Joe Rodriguez, MA, chair of Totino Grace's department of physical education and health and head cross-country running coach, says it's difficult making blood donation recommendations to student-athletes. Though giving blood is itself a teaching opportunity, Rodriguez says he would rather err on the side of keeping student-athletes safe. "My policy is to tell them what happens physiologically when they do give blood, and let them decide," he says, pointing to a need for more hard evidence and double-blind studies. "This needs to be clarified by someone with more authority than just a coach," he says.

Active people and athletic administrators often turn to physicians for advice; however, few studies on blood donation and exercise have been published. More often, recommendations are based on what physicians know about basic hematology and exercise physiology. After donating 450 mL (1 U) of whole blood, plasma volume falls 7% to 13%, then recovers within 24 to 48 hours. The hemoglobin level decreases by 10 to 20 g/L. With an adequate iron supply, hemoglobin returns to baseline after 3 to 4 weeks (1).

Competitive Athletes
It seems clear that blood donation is contraindicated for endurance athletes who will soon be competing. In a recent report (2), E. Randy Eichner, MD, a hematologist and internist in Oklahoma City, and editorial board member of The Physician and Sportsmedicine, contrasts the physiologic effects of blood doping with those of blood donation, and maintains that blood donation is "ergolytic" for competitive athletes.

He notes that many variables make it difficult to predict how much or how long donating a pint of blood will affect athletic performance. However, he notes that recovery after blood donation is fairly fast. Eichner writes: "In my anecdotal experience, maximal performance can return to normal within 1 to 2 weeks, and surely returns to normal after 3 to 4 weeks."

A study (3) on the effects of blood donation on 10 competitive cyclists before and after donating 1 U of blood found that maximal performance was decreased for at least 1 week after blood donation. (Cyclists were measured at baseline and at 2 hours, 2 days, and 7 days after phlebotomy.) Although researchers found that maximal performance was decreased, submaximal performance was unaffected.

Exercisers and Recreational Athletes
Marvin Adner, MD, a hematologist and internist in Framingham, Massachusetts, and medical director of the Boston Marathon, says that blood donation should not be a concern for active people who are not world-class athletes--as long as they are not iron deficient. He notes that though hemoglobin values will be lower than normal a few weeks after donation, blood donation does not erode fitness effects.

Adner cautions active people who donate blood to avoid taking regular iron supplements unless they are iron deficient from giving blood. Iron intake can cause symptoms in patients who have hereditary hemochromatosis. Iron supplements can also mask the anemia of colon cancer and damage the heart. "Unfortunately, many athletes--especially those who don't eat red meat--have borderline iron deficiency," he says.

Donald M. Christie, Jr, MD, an internist and sports physician in Lewiston, Maine, says hydration is the best recovery strategy. Donors need to drink not only what is offered afterward at the blood donation center, they need to aggressively hydrate over the remainder of the day, says Christie, who is an editorial board member of The Physician and Sportsmedicine. "Noting the color of the urine is a good way to gauge hydration status," he says.

He advises endurance athletes to think of the blood donation day as a rest day, and to tread cautiously the next day because hydration stores may not be replenished and delayed vasovagal effects may occur. Christie says though the performance decrement would be slight in an endurance athlete, blood donation should have virtually no effect on strength or short-burst activities.

In a study (4) that sought to determine the effects of blood donation on older exercisers, researchers measured submaximal and maximal working capacity and blood viscosity in younger donors, older donors, and older controls the day before and after blood donation. They found that mean submaximal and maximal values increased the day after donation in all groups, but that increases were only significant in the younger donors. Plasma viscosity decreased significantly in both donor groups. The authors concluded that a single blood donation did not alter the physical fitness of otherwise healthy people.

Lisa Schnirring, Minneapolis


Mollison FL, Engelfried CP, Contreras M: Blood Transfusion in Clinical Medicine, ed 8. Boston, Blackwell Scientific Publications, 1987 Eichner ER: Donating blood: altruistic but ergolytic. Sports Med Digest 2001;23(3):25 Panebianco RA, Stachenfeld N, Coplan NL, et al: Effects of blood donation on exercise performance in competitive cyclists. Am Heart J 1995;130(4):838-840 Janetzko K, Bocher R, Klotz KF, et al: Effects of blood donation on the physical fitness and hemorheology of healthy elderly donors. Vox Sang 1998;75(1):7-11

3. Ask the Doctor - with Prentice Steffen


By Prentice Steffen, MD, FAAEM

This report filed November 19, 2003

Dear Doc;
I have been wondering about how donating blood can affect an athlete's performance. Obviously, in the short term after a blood donation, performance will be hindered, since there is less blood to carry the oxygen around. But what about long-term effects?

How long after a blood donation does one's body typically recover? Is there any type of "super-compensation" that may occur from continued training after a donation? In other words, will continually putting a high demand on my cardiovascular system after donating cause my body to regenerate more red blood cells than I had before the donation?

Not that I will roll donating blood into my training program as a way to build more red blood cells, just curious. Will donating via aphaeresis help recovery?

I haven't donated blood for a few years. The last time I did, I went for a ride the following day, and really struggled. I would like to begin donating again, I just worry about how it will affect my performance as an athlete, particularly during the racing season. Thanks for entertaining my question.

Tony McCray
Portland, Oregon

Dear Tony;
What a great question! You are truly a gentleman, scholar, cyclist and all-around altruist. As a doctor, I believe that donating blood is one of the kindest and most generous acts that any of us can perform. Fortunately, your question has been studied to some extent, so I hope I'll be able to provide you with some useful advice.

When you give blood, about 450cc of whole blood is taken. As points of reference, a typical bike water bottle holds 600cc and a can of Coke contains 355 cc. Your 450cc donation represents about 10 percent of all the blood in you at any one time, so it's not a lot but it's not a little either. I've had riders worry about giving even two or three small blood tubes for UCI testing!

You can expect this donation to lower your hematocrit by about three percentage points. As you probably know, hematocrit is the measurement of the volume of your blood taken up by the red blood cells. The rest of the space is taken up by plasma, white blood cells, platelets, clotting factors and other miscellaneous molecules.

In the best study I found on this topic, a group of researchers took 10 male "amateur competitive cyclists" and measured heart rate (HR), VO2max, power output (in watts), and ventilatory threshold (VTh) during a standardized incremental exercise study. They tested each cyclist at four time points relating to a blood donation: One week before; two hours after; two days after, and seven days after. These researchers found that at maximal efforts all performance measurements were adversely affected at all three post-donation time points. For example, at the two hours and the two days testing, VO2max was down about eight percent. Even at seven days post-donation, the average VO2max was only improved to about seven percent down from pre-donation baseline testing. It's too bad they didn't test at subsequent 1-week intervals, but it's reasonable to speculate that a complete return to baseline might take as much as three to four weeks, or even a bit longer.

This research also demonstrated another important by showing that all submaximal measurements we not affected by the blood donation. Performance was only hurt at maximal effort. That's interesting because most of us, and even pros for that matter, spend the vast majority of our training time in submaximal zones.

So here's what I'd advise to different groups of cyclists:

Elite amateur and professional: Do not give blood. The detriment to performance is too great. Even during the off-season, you don't need this. As well an out-of-competition blood test would certainly turn up suspicious results due to alterations of serum EPO levels and reticulocyte counts. You really don't need this.

Competitive amateur: Off-season blood donations would be fine. I've long had a somewhat New Age theory that it would be good to donate blood because it would create sort of a cleansing turnover effect. I've seen nothing scientific written to support this idea.

Serious recreational: There is no reason that I can see not to donate blood on a regular basis. Blood centers advise every eight weeks maximum. Giving blood every 12 weeks might be more reasonable for this group.

Casual: Get out there and give every eight weeks to help make up for the fanatic riders described above!

General advice about the actual blood donation:

On the day before, do whatever you want. I usually time a donation to fall the day after a fairly hard series of workouts.
Don't do any workout the day of the donation.
An easy spin the day after should be fine and perhaps beneficial.
Hydrate well the day before, the day of and days following your donation.
Regular blood donors (more than two to three times a year) need regular ron supplementation. I recommend a daily multivitamin with iron plus an iron supplement. I use iron sulfate 140mg (28mg of elemental iron) three days a week. Also consider a nice steak dinner the day of or after the donation.
I found nothing that relates practically or theoretically to your question about a "super-compensation" effect. I can't think how or why that would occur and I'm fairly certain that it doesn't.

Finally, aphaeresis (aka, pheresis) refers to the taking of only certain parts out of the whole blood and returning the rest to the donor. The big three "pheresises" are plasmapheresis (only the plasma is kept), pateletpheresis (plateletes), and leukophoresis (white blood cells). Since athletic performance is all about the red blood cells, this is a great option for you and any athlete. The most common seems to be plateletpharesis as there is a great need for platelets to be transfused to cancer patients on chemotherapy. While there are medications to stimulate red and white blood cell production in these patients, there is nothing to replace the platelets which are needed to prevent serious bleeding episodes such as a brain hemorrhage. Plateletpheresis takes about two hours compared to the hour or so for a traditional blood donation. My local blood center here in San Francisco has special "e-chairs" (yes, internet connection and DVDs) for platelet donors.

So thanks a million for you question. I hope I've answered your questions and that you and many others will pursue this very important option. They don't call blood donation "the gift of life" for nothing.

For more information and to find your local blood center, go to or

4. Effects of Blood Donation

From Runing Times Newsletter

Q: I just donated blood via a process that takes both platelets and red blood cells. How long does it normally take the body to replace the red blood cells and fluids lost, and therefore restore its oxygen carrying capacity?

A: Thanks for donating blood. The loss of hemoglobin will have its greatest effect when cardiac demands are the greatest - during high-intensity workouts. The impact will decrease as intensity decreases, so the impact on an easy run should not be significant. Because blood donation will affect your ability to train intensely for a while, you don't want to do this right before a race. It takes about 120 days for the body to make new red blood cells - the cells which contain hemoglobin. Supplementing your diet with iron after blood donation will help maximize your iron stores. (There is a small segment of the population with excessive iron levels - hemochromatosis. These people should not supplement their iron intake. Even though their blood is rich in iron, it cannot be used in blood donation).

Remaining well hydrated will allow your body to rapidly replace the fluid that is lost during blood donation. --Cathy Fieseler, MD

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